Ask the Mechanic

Tight Valve Clearances

I have a club car side-by-side with a Kubota engine. The valve cover gasket started leaking, and I thought I would adjust the valves while I had the valve cover off. I noticed on the valve cover that the specs were given for the valve setting. I was surprised to see that the clearance for both valves was a small .0165 mm. I have never seen valve clearance this tight. Is this setting correct? It seems to me that especially the exhaust valve would "grow" more than that from heat and normal pounding of the face of the valves on the valve seats.

STEVE: I am with you on the valve clearance on that engine. It does seem small in relation to most other engines that I have set the valves. However, I have found that when I "run" the valves on one of the Kubota engines, the setting seems to have held specs. Since valve-setting directly affects engine timing, I always stay with manufacturer's specs. I called a Kubota dealer and asked about that small valve "lash," and he told me that he thought it was because the valve stems are very short and do not expand much. He also said that he thought the valve seats were extremely hard. It seems that the valve springs are not excessively strong, allowing far less force of the face of the valve on the valve seat.

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-- Write Steve Thompson at Ask The Mechanic, 2204 Lakeshore Dr., Suite 415, Birmingham, AL 35209, or email mechanic@progressivefarmer.com

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